htdbm - Manipulate DBM password databases

htdbm is used to manipulate the DBM format files used to
store usernames and password for basic authentication of HTTP users via
mod_authn_dbm. See the dbmmanage
documentation for more information about these DBM files.

Use batch mode; i.e., get the password from the command line
rather than prompting for it. This option should be used with extreme care,
since the password is clearly visible on the command
line. For script use see the -i option.

-i

Read the password from stdin without verification (for script usage).

-c

Create the passwdfile. If passwdfile already
exists, it is rewritten and truncated. This option cannot be combined with
the -n option.

-n

Display the results on standard output rather than updating a
database. This option changes the syntax of the command line, since the
passwdfile argument (usually the first one) is omitted. It
cannot be combined with the -c option.

-m

Use MD5 encryption for passwords. On Windows and Netware, this is
the default.

-B

Use bcrypt encryption for passwords. This is currently considered to
be very secure.

-C

This flag is only allowed in combination with -B (bcrypt
encryption). It sets the computing time used for the bcrypt algorithm
(higher is more secure but slower, default: 5, valid: 4 to 31).

-d

Use crypt() encryption for passwords. The default on all
platforms but Windows and Netware. Though possibly supported by
htdbm on all platforms, it is not supported by the
httpd server on Windows and Netware.
This algorithm is insecure by today's standards.

Use plaintext passwords. Though htdbm will support
creation on all platforms, the httpd daemon will
only accept plain text passwords on Windows and Netware.

-l

Print each of the usernames and comments from the database on
stdout.

-v

Verify the username and password. The program will print a message
indicating whether the supplied password is valid. If the password is
invalid, the program exits with error code 3.

-x

Delete user. If the username exists in the specified DBM file, it
will be deleted.

-t

Interpret the final parameter as a comment. When this option is
specified, an additional string can be appended to the command line; this
string will be stored in the "Comment" field of the database, associated
with the specified username.

filename

The filename of the DBM format file. Usually without the extension
.db, .pag, or .dir. If
-c is given, the DBM file is created if it does not already
exist, or updated if it does exist.

username

The username to create or update in passwdfile. If
username does not exist in this file, an entry is added. If it
does exist, the password is changed.

password

The plaintext password to be encrypted and stored in the DBM file.
Used only with the -b flag.

One should be aware that there are a number of different DBM file
formats in existence, and with all likelihood, libraries for more than
one format may exist on your system. The three primary examples are
SDBM, NDBM, GNU GDBM, and Berkeley/Sleepycat DB 2/3/4. Unfortunately,
all these libraries use different file formats, and you must make sure
that the file format used by filename is the same format that
htdbm expects to see. htdbm currently has
no way of determining what type of DBM file it is looking at. If used
against the wrong format, will simply return nothing, or may create a
different DBM file with a different name, or at worst, it may corrupt
the DBM file if you were attempting to write to it.

One can usually use the file program supplied with most
Unix systems to see what format a DBM file is in.

htdbm returns a zero status ("true") if the username and
password have been successfully added or updated in the DBM File.
htdbm returns 1 if it encounters some problem
accessing files, 2 if there was a syntax problem with the
command line, 3 if the password was entered interactively and
the verification entry didn't match, 4 if its operation was
interrupted, 5 if a value is too long (username, filename,
password, or final computed record), 6 if the username
contains illegal characters (see the Restrictions
section), and 7 if the file is not a valid DBM password
file.

Adds or modifies the password for user jsmith. The user
is prompted for the password. If executed on a Windows system, the password
will be encrypted using the modified Apache MD5 algorithm; otherwise, the
system's crypt() routine will be used. If the file does not
exist, htdbm will do nothing except return an error.

htdbm -c /home/doe/public_html/.htdbm jane

Creates a new file and stores a record in it for user jane.
The user is prompted for the password. If the file exists and cannot be
read, or cannot be written, it is not altered and htdbm
will display a message and return an error status.

htdbm -mb /usr/web/.htdbm-all jones Pwd4Steve

Encrypts the password from the command line (Pwd4Steve)
using the MD5 algorithm, and stores it in the specified file.

Web password files such as those managed by htdbm should
not be within the Web server's URI space -- that is, they should
not be fetchable with a browser.

The use of the -b option is discouraged, since when it is
used the unencrypted password appears on the command line.

When using the crypt() algorithm, note that only the first
8 characters of the password are used to form the password. If the supplied
password is longer, the extra characters will be silently discarded.

The SHA encryption format does not use salting: for a given password,
there is only one encrypted representation. The crypt() and
MD5 formats permute the representation by prepending a random salt string,
to make dictionary attacks against the passwords more difficult.

Notice:This is not a Q&A section. Comments placed here should be pointed towards suggestions on improving the documentation or server, and may be removed again by our moderators if they are either implemented or considered invalid/off-topic. Questions on how to manage the Apache HTTP Server should be directed at either our IRC channel, #httpd, on Freenode, or sent to our mailing lists.